Ideas to "Recharge the Battery" (hyperlink: rechargethebattery.org) include turning it into a park that connects with the street above, making an ice rink or skate park, a cellar for Washington wines or a mushroom farm.

One submission calls for an underground beach with full-spectrum lighting to make Seattleites feel better about winter.

Aaron Asis helps lead the effort which asked the public for ideas on what to do with the tunnel.

"Not to see it as a tunnel or the future of a tunnel but to see it as space," Asis said.

Erica Bush at the Downtown Seattle Association helped solicit ideas.

"It was really just a practice to get people engaged in coming up with fun different ideas for their public spaces," Bush said.

As fun as it might be to think about the future of the tunnel, which was built in the 1950s, the state and city are moving ahead on filling it in when the Alaskan Way Viaduct is torn down.

Asis wants the tunnel instead temporarily walled off, while people consider how to use it.

"Our hope is to just essentially hit the pause button on the Battery Street Tunnel portion so we can buy some time to maybe explore some ideas that might prove to be better use of public space and better use of public dollars," Asis said.

Doing something other than filling in the tunnel could be expensive.

The final environmental impact statement for the viaduct replacement project said, "While other uses of the old tunnel could be possible (such as pedestrian or bicycle use), the tunnel would require costly retrofits to meet current standards, including structural, seismic, and health and safety standards."

WSDOT spokeswoman Laura Newborn wrote, "The Washington State Transportation Department is legally obligated to follow the Final Environmental Impact Statement for the Alaskan Way Viaduct Replacement Program, which states the Battery Street Tunnel will be decommissioned."

The state expects to have a contractor selected early next spring to tear down the viaduct and fill in the old tunnel.